1. Field of the Invention
This invention relates to an enclosure for constructing prototype electrical and electronic devices.
2. Background Art
In the design of electrical and electronic circuits, particularly for circuit developers and students, commonly after the circuit design has been established, a prototype is built to test the operation and feasibility of the circuit design. The prototype not only must be functional to provide the required purposes, it must also be able to withstand various inadvertent mishaps in its handling during its construction with various electrical components, and changes of electrical components which may be required during its testing stage, as well as when submitting the prototype for evaluation by other people. In order to preserve the integrity of the circuit design, a secure protective project enclosure must be provided. Heretofore, rectangular plastic boxes are employed for fabricating prototype electrical and electronic devices. The rectangular plastic box normally consists of a simple rectangular plastic casing and a rectangular plastic top cover, or alternatively two U-shaped rectangular half shells engageable with one another as top and bottom half shells to form a rectangular box. Various openings must be cut by the prototype builder in the side, bottom and top panels of the box to accommodate the operating parts of various electrical components such as switches, connectors, power receptacles, rotary shafts of rheostats, and numerical or graphic displays, etc., which are commonly used in making an electrical circuit. These electrical components are usually mounted on a printed circuit board located inside the box. It has been very problematic in forming such openings in the various side, top and bottom panels of the plastic box since these openings are formed commonly by drilling, sawing, and cutting the plastic panels at the required locations; and the plastic panels can easily break or crack in the drilling, sawing and cutting processes. It is particularly problematic to carry out these processes with a relatively small size plastic box for use in enclosing a relatively small circuit design, because of the difficulties in retaining and mounting the small plastic box securely during the sawing, cutting and drilling processes. These processes are difficult and sometimes impossible to carry out due to the restricted space available for inserting the drill and/or the cutting tool inside a relatively small box. Moreover, in order to form any circular opening larger than the size of a standard drill bit, or in forming openings other than a circular shape, the opening must first be formed by marking the outline of the required opening on the plastic panel and then numerous holes are drilled along the outline, and then the area defined by the numerous holes is punched out to form the opening. The opening thus formed invariably has jagged edges. In order to refine the shape of the opening, the jagged edges must then be painstakingly filed down by hand to obtain the desirable smooth edges. Often the filing process would result in a rather ugly irregularly shaped opening which ultimately renders an inferior appearance in the prototype device.
Furthermore, when a printed circuit board is employed in fabricating the prototype circuit, the circuit board is normally mounted in a horizontal manner inside the lower casing with the control and display electrical components mounted on top of the printed circuit board. These components have rotary shafts and/or slidable handles which must extend outside of the top panel of the enclosure to facilitate their operations. Accordingly, openings must be formed at the exact locations in the top panel for this purpose. It is extremely difficult to determine and to mark on the top panel of the plastic box accurately at the exact locations for forming the openings for accommodating the rotary shaft and slidable handle of these control and display electrical components.
Furthermore, operation markings such as a scale must be provided adjacent to opening for the rotary shaft and the slidable handle of the control components to guide or indicate their operations. Such operation markings are also difficult to provide on the plastic surface. Normally, such markings are either provided on an adhesive label applied on the plastic surface and located adjacent to the openings, or alternatively the markings are inscribed directly on the plastic surface adjacent to the openings. Since an adhesive label can easily fall off due to the deterioration of the adhesive or it may be defaced, while inscriptions of markings are difficult and time consuming to make, or to engrave neatly on the plastic surface.
Also, due to the limited space available in the protective plastic box, many electrical components such as connectors, switches, connection jacks, are necessarily located along the narrow space between the printed circuit board and the side panels inside the box, and a plurality of electrical wiring must be employed for directly connecting between the connection terminals of these electrical components and the printed circuit board. The plurality of electrical wiring connections are time consuming to make, and the connections are unreliable due to the tendency of damaging the wiring or shorting of the connection terminals.